1. Technical Field
The present subject matter relates to semiconductor memory, and, more specifically, to controlling an access of a memory.
2. Background Art
Many types of semiconductor memory are known in the art. One type of memory is flash memory which stores charge in a charge storage region of a memory cell. The voltage threshold of the metal-oxide-semiconductor field-effect transistor (MOSFET) based flash cell can be changed by changing the amount of charge stored in the charge storage region of the cell, and the voltage threshold can be used to indicate a value that is stored in the flash cell. By providing a voltage across the flash cell that is between the voltage thresholds of the two different states of the flash cell, the state of the flash cell can be determined by measuring current flowing through the flash cell. A flash cell has a much higher on-current than off-current. One architecture in common use for flash memories is a NAND architecture. In a NAND architecture, two or more memory cells are coupled together into a string, with the individual cell control lines coupled to word lines. A NAND string may be coupled to a bit line at one end of the NAND string.
Another type of memory is phase change memory (PCM). PCMs utilize a phase change material having a non-conductive amorphous state and a conductive crystalline state. A PCM cell may be put into one state or the other to indicate a stored value. By providing a voltage potential across the PCM cell, the state of the PCM cell can be determined by measuring current flowing through the PCM cell. A PCM cell has a much higher on-current than off-current.
Many types of memory, including flash memory and PCM may organize the memory cells into an array with control lines that may cross the array in both the ‘X’ and ‘Y’ directions. While these control lines may have many different names, they may commonly be called word lines and bit lines. The control lines may be quite long and have a high resistance and capacitance due to their length and the number of memory cells coupled to the lines.